Installing policyrcd-script-zg2 doesn't quite do this because of the way
that live-build installs its own temporary version of policy-rc.d. The
only remotely sensible way I can see to deal with this is to create the
symlink manually.
We don't want the symlink to /run/systemd/resolve/stub-resolv.conf, and
launchpad-buildd will inject its own version if it doesn't get confused by a
symlink.
